Commit | Line | Data |
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00512bdd JH |
1 | /* |
2 | * Copyright (C) 2008 Imagination Technologies Ltd. | |
3 | * Licensed under the GPL | |
4 | * | |
5 | * Dynamic ftrace support. | |
6 | */ | |
7 | ||
8 | #include <linux/ftrace.h> | |
9 | #include <linux/io.h> | |
10 | #include <linux/uaccess.h> | |
11 | ||
12 | #include <asm/cacheflush.h> | |
13 | ||
14 | #define D04_MOVT_TEMPLATE 0x02200005 | |
15 | #define D04_CALL_TEMPLATE 0xAC200005 | |
16 | #define D1RTP_MOVT_TEMPLATE 0x03200005 | |
17 | #define D1RTP_CALL_TEMPLATE 0xAC200006 | |
18 | ||
19 | static const unsigned long NOP[2] = {0xa0fffffe, 0xa0fffffe}; | |
20 | static unsigned long movt_and_call_insn[2]; | |
21 | ||
22 | static unsigned char *ftrace_nop_replace(void) | |
23 | { | |
24 | return (char *)&NOP[0]; | |
25 | } | |
26 | ||
27 | static unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr) | |
28 | { | |
29 | unsigned long hi16, low16; | |
30 | ||
31 | hi16 = (addr & 0xffff0000) >> 13; | |
32 | low16 = (addr & 0x0000ffff) << 3; | |
33 | ||
34 | /* | |
35 | * The compiler makes the call to mcount_wrapper() | |
36 | * (Meta's wrapper around mcount()) through the register | |
37 | * D0.4. So whenever we're patching one of those compiler-generated | |
38 | * calls we also need to go through D0.4. Otherwise use D1RtP. | |
39 | */ | |
40 | if (pc == (unsigned long)&ftrace_call) { | |
41 | writel(D1RTP_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]); | |
42 | writel(D1RTP_CALL_TEMPLATE | low16, &movt_and_call_insn[1]); | |
43 | } else { | |
44 | writel(D04_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]); | |
45 | writel(D04_CALL_TEMPLATE | low16, &movt_and_call_insn[1]); | |
46 | } | |
47 | ||
48 | return (unsigned char *)&movt_and_call_insn[0]; | |
49 | } | |
50 | ||
51 | static int ftrace_modify_code(unsigned long pc, unsigned char *old_code, | |
52 | unsigned char *new_code) | |
53 | { | |
54 | unsigned char replaced[MCOUNT_INSN_SIZE]; | |
55 | ||
56 | /* | |
e9b349f0 LB |
57 | * Note: |
58 | * We are paranoid about modifying text, as if a bug was to happen, it | |
59 | * could cause us to read or write to someplace that could cause harm. | |
60 | * Carefully read and modify the code with probe_kernel_*(), and make | |
61 | * sure what we read is what we expected it to be before modifying it. | |
00512bdd JH |
62 | */ |
63 | ||
64 | /* read the text we want to modify */ | |
65 | if (probe_kernel_read(replaced, (void *)pc, MCOUNT_INSN_SIZE)) | |
66 | return -EFAULT; | |
67 | ||
68 | /* Make sure it is what we expect it to be */ | |
69 | if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0) | |
70 | return -EINVAL; | |
71 | ||
72 | /* replace the text with the new text */ | |
73 | if (probe_kernel_write((void *)pc, new_code, MCOUNT_INSN_SIZE)) | |
74 | return -EPERM; | |
75 | ||
76 | flush_icache_range(pc, pc + MCOUNT_INSN_SIZE); | |
77 | ||
78 | return 0; | |
79 | } | |
80 | ||
81 | int ftrace_update_ftrace_func(ftrace_func_t func) | |
82 | { | |
83 | int ret; | |
84 | unsigned long pc; | |
85 | unsigned char old[MCOUNT_INSN_SIZE], *new; | |
86 | ||
87 | pc = (unsigned long)&ftrace_call; | |
88 | memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE); | |
89 | new = ftrace_call_replace(pc, (unsigned long)func); | |
90 | ret = ftrace_modify_code(pc, old, new); | |
91 | ||
92 | return ret; | |
93 | } | |
94 | ||
95 | int ftrace_make_nop(struct module *mod, | |
96 | struct dyn_ftrace *rec, unsigned long addr) | |
97 | { | |
98 | unsigned char *new, *old; | |
99 | unsigned long ip = rec->ip; | |
100 | ||
101 | old = ftrace_call_replace(ip, addr); | |
102 | new = ftrace_nop_replace(); | |
103 | ||
104 | return ftrace_modify_code(ip, old, new); | |
105 | } | |
106 | ||
107 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) | |
108 | { | |
109 | unsigned char *new, *old; | |
110 | unsigned long ip = rec->ip; | |
111 | ||
112 | old = ftrace_nop_replace(); | |
113 | new = ftrace_call_replace(ip, addr); | |
114 | ||
115 | return ftrace_modify_code(ip, old, new); | |
116 | } | |
117 | ||
3a36cb11 | 118 | int __init ftrace_dyn_arch_init(void) |
00512bdd | 119 | { |
00512bdd JH |
120 | return 0; |
121 | } |